Function Headers

A function header names the return type, function name, and parameter list.

function_prototypes.c

#include <stdio.h>

int square(int value) {
    return value * value;
}

int main(void) {
    int value = ;
    int result = square(value);

    printf("square=%d\n", result);
    return 0;
}

#include <stdio.h>

int square(int value) {
    return value * value;
}

int main(void) {
    int value = ;
    int result = square(value);

    printf("square=%d\n", result);
    return 0;
}

#include <stdio.h>

int square(int value) {
    return value * value;
}

int main(void) {
    int value = ;
    int result = square(value);

    printf("square=%d\n", result);
    return 0;
}

header `int square(int value)` is the function header.

definition The function definition combines the header with the body that runs.